1. Field of the Invention
This invention relates to the field of optical data communications, and more particularly relates to a method and apparatus for reliably operating optical transceivers at 2.5 Gbps that are designed to operate at 1.25 Gbps.
2. Description of the Related Art
The use of optical communications is becoming increasingly prevalent in a wide array of applications that require high bandwidth. For example, today""s networks must carry vast amounts of information. High bandwidth applications supported by these networks include streaming video, streaming audio, and large aggregations of voice traffic. In the future, these bandwidth demands are certain to increase. To meet such demands, an increasingly popular alternative is the use of optical communications. The use of optical communications provides several benefits, including high bandwidth, low noise, ease of installation, and transparency for future growth.
Such optical communication systems transfer data at extremely high bit rates. To support these high bit rates, optical communications equipment often employs optical communications internally. The use of optical communications allows throughput to be more easily maintained, when compared to converting the incoming optical signals to electrical signals and subsequently distributing the electrical signals using copper cabling and/or printed-circuit boards. Thus, optical transceivers and cabling are often employed in transferring data from one section of the equipment to another, for example.
As transmission speeds have increased, however, the cost of optical transceivers has risen dramatically. Moreover, the cost/maturity curve for the higher-speed parts needed to meet these demands is flatter, indicating that the cost of such parts does not decrease as quickly with time as does that of lower-speed parts. Costs for such parts tends to be higher because yields, and so volume, is substantially lower in comparison to lower-performance parts. For example, the current cost of optical transceivers designed to operate at bit rates on the order of about 2.5 gigabits per second (Gbps) is approximately four to five times that of optical transceivers designed to operate at bit rates on the order of about 1 Gbps.
In light of the foregoing, it can be seen that providing high-speed optical communications at a relatively low cost is desirable.
A method and apparatus are described for operating optical transceivers, designed to operate at about 1 Gbps, at about 2.5 Gbps. In doing so, an optical transceiver according to the present invention provides high-speed optical communications at a relatively low cost.
In one embodiment of the present invention, an ultra-short-reach optical transceiver is described. The ultra-short-reach optical transceiver comprises an optical transmitter, an optical receiver, and a clock and data recovery unit. The optical transmitter is configured to transmit a first signal. Additionally, the optical transmitter is nominally designed to transmit data at a designed transmit bit rate of between about 0.9 Gbps and about 1.25 Gbps. The first signal preferably has a bit rate of between about 2 Gbps and about 3 Gbps, and exhibits an eye opening of at least about 50%. More preferably, the first signal preferably has a bit rate of about 2.488 Gbps, and exhibits an eye opening of at least about 70%. The optical receiver is configured to receive a second signal and is nominally designed to receive data at a designed receive bit rate of between about 0.9 Gbps and about 1.25 Gbps, and, nominally, at a bit rate of about 1 Gbps. The second signal has a bit rate of between about 2 Gbps and about 3 Gbps and, preferably, a bit rate of about 2.488 Gbps. The clock and data recovery unit is coupled to the optical receiver. The ultra-short-reach optical transceiver is configured to exchange data with another such ultra-short-reach optical transceiver over a fiber-optic cable of up to about 500 m in length.
In another embodiment of the present invention, a method of manufacturing an ultra-short-reach optical transceiver is described. First, an optical transceiver design for an optical transceiver is created. The optical transceiver is nominally designed to transmit at a transmit bit rate of between about 0.9 Gbps and about 1.25 Gbps (preferably 1 Gbps), and to receive at a receive bit rate of between about 0.9 Gbps and about 1.25 Gbps (preferably 1 Gbps). This is done via the design itself, choice of fabrication process and materials, and other manufacturing parameters within the designer""s control. Next, at least one optical transceiver is manufactured according to the optical transceiver design. A selected optical transceiver is then selecting from at least one optical transceivers manufactured. The selected optical transceiver is then tested, to determine if the selected optical transceiver is acceptable. This is accomplished by coupling the selected optical transceiver to an optical communications test unit with a fiber-optic cable and operating the selected optical transceiver at a transmit bit rate and a receive bit rate of between about 2 Gbps and about 3 Gbps, and, preferably, 2.488 Gbps. The fiber-optic cable is preferably up to about 500 m in length.
The foregoing is a summary and thus contains, by necessity, simplifications, generalizations and omissions of detail; consequently, those skilled in the art will appreciate that the summary is illustrative only and is not intended to be in any way limiting. Other aspects, inventive features, and advantages of the present invention, as defined solely by the claims, will become apparent in the non-limiting detailed description set forth below.